Fluid supply systems use motors to drive pumps and transfer fluids from supply reservoirs, such as wells, to demand reservoirs, such as tanks. A sensor measures a characteristic of the fluid, and a controller controls operation of the motor. In some systems, the controller measures a level of the fluid in a tank and controls operation of the motor to maintain the level within a range. When the level reaches the low end of the range, the controller turns the motor on and keeps it on until the level reaches the high end of the range. In other systems, the speed of the motor is controlled to maintain pressure within predetermined parameters. A variable speed loop controls the speed of the motor within a variable speed range to gradually increase or decrease the pumping rate and thereby maintain the pressure near the setpoint. Induction motors are frequently used in fluid supply systems.